The head of the NSW anti-corruption agency, Megan Latham, has been asked to explain why she has refused to lift a suppression order preventing former state mining minister Ian Macdonald revealing what he told the agency in submissions.

The request for an explanation was made by David Levine, ICAC’s independent inspector, and came soon after The Australian revealed on September 25 that ICAC did not make public evidence given by witnesses, including federal Labor frontbencher Anthony Albanese, that favoured Mr Macdonald.

Mr Levine has asked Ms Latham to provide him with material that would explain how she decided it was not in the public interest to lift the suppression order.

Mr Macdonald, who is facing charges of misconduct in public office over the allocation of coal exploration licences, has tried repeatedly to have the suppression order lifted so he can use the information he provided to ICAC to explain actions that led to criminal charges.

ICAC found he had acted corruptly by issuing a licence to Doyles Creek Mining, a company then chaired by former union official John Maitland.

He has been charged with misconduct in public office and his case is due for mention on Friday in the NSW Supreme Court.

Mr Levine’s interest in the basis for ICAC’s continued ­suppression of Mr Macdonald’s submissions has come to light soon after the inspector’s annual report warned the agency against projecting “an almost breathtaking arrogance in relation to its own powers”. On June 23, ICAC’s principal solicitor, Patrick Broad, told Mr Macdonald’s lawyers that Ms Latham had rejected their latest attempt to have the suppression order lifted.

She had carefully considered their application but “is not satisfied that it is in the public interest to do so”.

However, Mr Levine wrote to Ms Latham on October 13 pointing out the agency was not to issue a suppression order under section 112 of the ICAC Act unless it was satisfied that this was “necessary or desirable” in the public interest.

“I write to ask whether you would be good enough to inform me whether there is any case law, convention, practice manual or similar mat­erial that aids the determination of an application for a direction under section 112,” he wrote.

He also asked whether there were particular factors taken into account on the question of “necessity” or “desirability”.

The dispute over Ms Latham’s refusal to lift the suppression order comes after a separate dispute over the suppression of evidence involving former ICAC commissioner David Ipp.

On June 17, Mr Macdonald’s lawyers complained to Mr Levine that Mr Ipp had refused to allow transcripts of private hearings to be made public.

“The difficulty with not releasing it is that ICAC is, in effect, choosing which evidence to present,” said Mr Macdonald’s law firm, Bilbie Dan.

“ICAC withheld considerably exculpatory evidence of events and actions by the department, industry and ministers which is exculpatory for Mr Macdonald.”